Two-component coating systems and compositions based on polyurethanes and/or polyureas are widely used in industry because of the many advantageous properties exhibited by these coating chemistries. Two-component coating systems generally comprise a liquid binder component and a liquid hardener/crosslinker component. The liquid binder component may comprise an isocyanate-reactive component such a polyol or polyamine, and the liquid crosslinker component may comprise a polyisocyanate component. The addition reaction of the polyisocyanate component with the isocyanate-reactive component, produces highly crosslinked polyurea and/or polyurethane networks that form coating films when applied to substrates.
The reaction of polyisocyanates with polyamines results in highly crosslinked polyurea coatings that exhibit excellent mechanical and chemical resistance properties (e.g., abrasion, solvent, and weathering resistance). However, primary polyamines and polyisocyanates generally react together very rapidly to produce polyureas. Often, therefore, typical pot lives or gel times of two-component polyurea coating compositions are only between several seconds and a few minutes. Thus, polyurea coatings often cannot be applied manually, but must be applied using specialized spray equipment that accurately meters and mixes the binder and crosslinker components immediately before spray application.